1. Field of the Invention
This invention relates to electrical connectors for high frequency environments and more particularly it concerns novel patch cord type connectors for use in multiple access wiring systems for computer networks.
2. Description of the Prior Art
It is known to provide computer systems with a plurality of separate but mutually interconnected terminals or work stations. In fact, many buildings are now wired with computer lines leading to several locations so that computer work stations may be connected to each other and to centralized computer facilities according to the particular needs of the occupants. As the occupants or their needs change, it is often necessary to rearrange the organization of the wiring between the computer work stations and the centralized computer facilities. This is done by means of patch cords which interconnect connector blocks located in a wiring closet in the building.
For economy of space, particularly since it is often necessary for very large numbers of computer terminals to be accommodated to many different systems and configurations, the patch cord connections must be arranged very close to each other. This close spacing of patch connectors has raised problems because computer systems operate at very high frequencies and the signals from one set of connectors may interfere with and degrade the quality of the signals on an adjacent set of connectors. This problem, sometimes referred to as "cross talk", becomes more severe as the connectors are positioned closer to each other.
U.S. patent application No. 07/719,939, filed Jun. 24, 1991, now U.S. Pat. No. 5,160,273, and assigned to the assignee of the present invention, discloses novel connector blocks which maintain closely spaced wiring terminals for selective interconnection. Each pair of terminals in these connector blocks is formed with spring finger which are normally in contact but are spread apart when a printed circuit board is inserted between them. The block itself, which is made of molded plastic, is provided with internal electrically conductive shields. These shields are arranged in the block to provide electromagnetic isolation between groups of terminals and associated spring fingers.
A need for further electromagnetic isolation arises when the connector block is used as a patching device. In that case the printed circuit boards inserted between the spring fingers are provided with patching cables which in turn connect the spring fingers to computer terminals or work stations. Before a printed circuit board is inserted, the normally contacting spring fingers in each pair are mutually short circuited and need not be electromagnetically isolated from each other. However when the printed circuit board is inserted to separate the spring fingers and connect them to a computer work station, the signals on the now separated spring fingers are no longer the same and they must therefore be electromagnetically isolated from each other.
A further problem which occurs in the use of connector blocks in patching systems is the maintenance of a continuous ground shield throughout the system. Although the various cables used in the system have electrically conductive sheaths which are connected to ground terminals at one end or the other, the arrangements known up to now did not provide for a continuous ground from the centralized computer facility through the patch connector blocks to the individual computer work stations.